It has been shown that brain and other tissues can produce free isoprenoid alcohols such as farnesol, as well as cholesterol, in vitro. These alcohols result from the action of a pyrophosphorylated alcohol. Such an enzymatic action could provide a control point in central nervous system cholesterol biosynthesis. Information thus far has indicated the presence of a potent pyrophosphatase acting in CNS tissue in vitro. It is the purpose of the proposed studies to evaluate the role of this pyrophosphatase in vitro and in vivo in CNS tissue and study its characteristics. The latter will lead to isolation and purification of the enzyme(s) and determination of its importance in the CNS cholesterol biosynthetic pathway.